This study subserves the long-term commercial objective of marketing the Comprehensive Motion Apparatus (CMA) with an indication for attention-deficit/hyperactivity disorder (ADHD). Parents, policy makers, and even professionals who are reluctant to give stimulants to children should welcome an effective non-drug treatment for this common disorder. The market is large and international, involving 3-8% of children. The goal of this proposal is to determine the effectiveness of CMA motion stimulation for ADHD. Previous controlled studies of simple rotary stimulation, including two in children with ADHD, confirmed clinical observations suggesting moderate beneficial effects. CMA stimulation is multidimensional compared with previously studied rotary stimulation. Preliminary open data suggest CMA effectiveness. The proposed Phase I study will randomly assign 50 children with rigorously diagnosed ADHD to either 12 weeks of comprehensive motion stimulation or a control condition of equal length and intensity, utilizing the same setting. Outcome will be assessed by parent and teacher ratings and neuropsychological tests before, during and after treatment. Moderation and mediation by vestibular function will be examined by pre- and post-tests of vestibular function. We hypothesize that CMA stimulation will show a larger effect than simple rotary stimulation, significant compared to sham control. Sufficient sample size is assured by the Ohio State University's recruitment record.